This invention relates to an apparatus for in-line surface finishing elongate cylindrical stock, for example, stainless steel tubing, and a method for in-line surface finishing of cylindrical stock such as stainless steel tubing. Use of the term xe2x80x9cin-linexe2x80x9d is used in this application to mean that the scratch pattern of the surface finish applied to the stock extends substantially parallel to, or linearly along, the longitudinal axis of the stock. Applicant""s prior patent, U.S. Pat. No. 5,759,089, for example, discloses an apparatus and method for buffing the surface of stainless steel tubing to achieve a chrome-bright finish. The scratch pattern extends generally along the length of the tubing. However, the buffing process described in the above-referenced patent ramdomizes the scratch pattern by randomly-oscillating the buffing wheels across the surface of the tubing while reducing the scratches to the point where they are essentially invisible to the naked eye. Tubing finished in this manner has numerous mechanical and ornamental applications, including railing and ladders for boats, exterior vehicle accessories, and metal furniture structural pieces such as legs and arms.
However, other applications require a xe2x80x9cbrushedxe2x80x9d look. For example, many commercial and residential appliances such as stoves, refrigerators now have a brushed steel finish. Such unpainted brushed finishes have recently become more popular as more expensive residential appliances are designed to resemble commercial cooking equipment. However, certain parts such as handles cannot presently be machine-processed to impart a brushed finish which will match the brushed finish on the doors, sides top and other visible surfaces. Thus, it is presently necessary for matching handles and the like to be hand finished. This is done manually by pressing the object against a polishing wheel covered with polishing paper with a grit which applies a long scratch along the longitudinal axis of the object.
This prior art practice presents several disadvantages, including the expense of carrying out this process manually instead of automatically and the variability of quality and appearance resulting from variation in the skill of the person carrying out the process.
The apparatus and process described comes near the end of a number of other prior art processes, the major ones being described briefly below.
In general, coiled stainless steel sheet between 18 inches and 60 inches wide and 5,000 feet long is slit into a strip which is as wide as the circumference of the tubing to be formed. For example, tubing having an O.D. of one inch will be slit into a strip 3.1416 inches wide. The strip is rolled back into a coil and taken to a tube mill. The tubing is formed by traversing the strip in a continuous process through a series of forming rollers. The initial stage is referred to as the xe2x80x9cbreakdownxe2x80x9d stage, where the opposing edges are turned upwardly.
The strip is then passed to a xe2x80x9cfinxe2x80x9d section, where the opposing edges are gradually and progressively curved upwardly towards each other until the strip has been formed into a closed cylindrical tube with the opposing edges aligned with each other.
The tube is passed through a welding machine where the two opposing edges are continuously welded to each other. The welded tube then passes through a grinder where the weld is ground flush with the adjacent walls of the tube. The tube is then passed through a precision-sizing section where a series of precisely sized and aligned sizing rollers shape the tubing to its final size and cylindrical shape.
The tubing is then cut to a predetermined manageable length, for example, 30 feet, for further processing.
In some prior art processes, the tubing is then polished. xe2x80x9cPolishingxe2x80x9d is a term of art which means using progressively finer- grit sandpaper to put an initial smooth finish on the exterior surface of the tubing. The sandpaper is applied to the tubing as the tubing is rotated. Thus, a radial finish is applied to the tubing during this process. The scratch pattern formed during this process extends radially around the outer circumferential surface of the tubing and are quite easily seen when light is reflected off of the tube. In relative terms, polishing applies a finish where the scratch pattern is clearly visible and, as described above, is desirable when a brushed look is needed. However, the radial pattern applied by prior art machine polishing processes is clearly undesirable, since it does not match the long scratch pattern of brushed stainless steel used on commercial and high end residential appliances.
The apparatus and method disclosed in this application polishes stainless steel tubing xe2x80x9cin-linexe2x80x9d at commercial speeds to a brushed finish which exhibits a highly desirable ornamental appearance wherein the visible scratches extend generally longitudinally along the length of the stainless steel tubing to which the finish is applied.
Therefore, it is an object of the invention to provide an apparatus for in-line surface finishing elongate cylindrical stock.
It is another object of the invention to provide an apparatus for in-line or linear surface finishing stainless steel tubing.
It is another object of the invention to provide an apparatus for in-line polishing of stainless steel tubing.
It is another object of the invention to provide an apparatus for polishing stainless steel tubing without applying a radial scratch pattern to the outer surface of the tubing.
It is another object of the invention to provide an apparatus for polishing stainless steel tubing which operates a speeds compatible with other commercial stainless steel tubing manufacturing steps.
It is another object of the invention to provide a method for in-line surface finishing of cylindrical stock such as stainless steel tubing which achieves a brushed finish wherein the scratch pattern extends longitudinally along the length of the tubing and thus avoids the appearance of rings around the tubing characteristic of prior art machine polishing processes.
These and other objects of the present invention are achieved in the preferred embodiments disclosed below by providing a surface finishing apparatus for in-line outer surface polishing of elongate cylindrical metal stock to apply a long scratch finish, comprising a stock feeder for feeding a length of stock through the finishing apparatus from an infeed downstream to an outfeed position while rotating the stock about its longitudinal axis and a polishing assembly for finish-treating the outer surface of the stock as the stock is fed through the apparatus to apply a long scratch finish thereto. The polishing assembly comprises a rotatable finishing wheel having a finish-treating peripheral surface for being applied in an in-line orientation against the outer surface of the stock as the stock is simultaneously fed and rotated through the finishing apparatus. The finishing wheel is mounted on an axis of rotation which is perpendicular to the longitudinal axis of the stock, and is rotated at a speed sufficiently great in comparison to the speed of rotation of the stock that the scratch finish applied to the stock is linear and extends substantially along the longitudinal axis of the stock.
According to one preferred embodiment of the invention, the apparatus includes second and third rotatable finishing wheels positioned downstream of the finishing wheel for altering the finish applied by the finishing wheel.
According to another preferred embodiment of the invention, a stock-engaging backup support is positioned for engagement with the rotating stock against the direction of rotation of the stock for preventing lateral displacement of the stock by the stock rotating wheel.
According to yet another preferred embodiment of the invention, each of the finishing wheels is vertically positioned above the stock for being applied against an upper surface of the rotating stock.
According to yet another preferred embodiment of the invention, an adjustment apparatus is provided for adjusting the vertical position of the finishing wheel relative to the stock.
According to yet another preferred embodiment of the invention, the stock rotating wheel comprises a drive roller mounted between the infeed position and the outfeed position on an axis in non-parallel alignment with the longitudinal axis of travel of the stock for rotation in a direction having a component diagonal to the direction of travel of the stock through the finishing apparatus for simultaneously rotating and feeding the stock downstream to the outfeed position, the driver roller positioned to support the stock and rotate the stock by surface-to-surface driving contact between the outer surface of the stock and an outer, driving surface of the drive roller.
According to yet another preferred embodiment of the invention, a plurality of pairs of guide rollers is positioned along the length of the finishing apparatus between the infeed position and the outfeed position for positioning and maintaining the stock therebetween and in finishing position in relation to the finishing wheels.
According to yet another preferred embodiment of the invention, the finishing wheel supports on its contact surface with the stock a belt having a finishing surface thereon, the belt carried for rotation on the finishing wheel and at least one supporting idler wheel.
According to yet another preferred embodiment of the invention, the finish-treating peripheral surface of the finishing wheel is selected from a group of finish treating materials consisting of sisal, and a synthetic polishing material.
According to yet another preferred embodiment of the invention, the finishing wheel applies an initial cut finish to the stock, the second finishing wheel applies a finish cut to the stock and the third finishing wheel applies a blending finish to the stock.
According to yet another preferred embodiment of the invention, a tension adjustment apparatus is provided for adjusting the tension of the belt against the finishing wheel.
An embodiment of the method of in-line outer surface polishing of elongate cylindrical metal stock to apply a long scratch finish according to the invention comprises the steps of feeding a length of stock from an infeed downstream to an outfeed position while rotating the stock about its longitudinal axis;
According to yet another preferred embodiment of the invention, a finish treatment is applied to the outer surface of the stock as the stock is fed, the finish-treating step being applied in an in-line orientation against the outer surface of the stock as the stock is simultaneously fed and rotated on an axis of rotation which is perpendicular to the longitudinal axis of the stock wherein the finish-treating step as applied at a speed sufficiently great in comparison to the speed of rotation of the stock that the scratch finish applied to the stock is linear and extends substantially along the longitudinal axis of the stock.
According to yet another preferred embodiment of the invention, the method includes the steps of applying second and third finish treatments to the stock downstream of the finish treatment for altering the finish applied to the stock.
According to yet another preferred embodiment of the invention, the method includes the step of engaging the rotating stock against the direction of rotation of the stock for preventing lateral displacement of the stock as it rotates.
According to yet another preferred embodiment of the invention, the method includes the step of applying the finishing treatments with wheels having respective finish-applying surfaces vertically positioned above the stock for being applied against an upper surface of the rotating stock.
According to yet another preferred embodiment of the invention, the method includes the step of adjusting the vertical position of the finishing wheel relative to the stock for varying the pressure at which the finish is applied to the stock.
According to yet another preferred embodiment of the invention, the step of rotating the stock includes the step of engaging the stock at an axis in non-parallel alignment with the longitudinal axis of travel of the stock for rotation in a direction having a component diagonal to the direction of travel of the stock for simultaneously rotating and feeding the stock downstream to the outfeed position.
According to yet another preferred embodiment of the invention, the method includes the step of supporting the stock on a plurality of pairs of guide rollers positioned between the infeed position and the outfeed position as it is fed and rotated.
According to yet another preferred embodiment of the invention, the step of applying the finish treatment comprises the step of supporting an endless belt having a finish treatment-applying surface thereon on a rotating finish wheel which engages the stock.
According to yet another preferred embodiment of the invention, the method includes the step of supporting the belt on a pair of idler rollers positioned upstream and downstream, respectively, of the rotating finish wheel, the idler rollers being positioned to the area of contact between the belt and the stock to increase the length of the scratch finish applied to the stock.
According to yet another preferred embodiment of the invention, the method includes the steps of the finishing wheel applying an initial cut finish to the stock, the second finishing wheel applying a finish cut to the stock and the third finishing wheel applying a blending finish to the stock.